Depending on the property and it's policy, you can sometimes find out your theo by asking a host. Once you know your coin in and theo, you can calculate what the casino calculates as their hold for a particular game.
In our experience, that number is always more than the manufactuere's hold for that pay schedule. Sometimes the difference is nominal; sometimes way off the mark in the players favor. For example, a year ago I was playing $1 9/6 JoB with .3% CB yet that particular casino was calculating a 8% hold for comp purposes. From the players perspective, that was a $32 theo loss on $20k coin in. From the casino's perspective, they figured you were worth $1,600 to them which always meant $500-600 in comps. Even at retail, this was (and maybe still is) a strong deal. This level of play also warranted a FP mailer worth $200-300 every 2-3 months. Nothing to live on but a very strong deal nonetheless.
The key is to find games in a casino in which they value the hold at a significantly higher amount than the game actually is. If you're not giving up too much of an advantage, you can easily make up in worthwhile, real dollar comps significantly more than your theo loss. Access to this info varies by property, host and even machine despite offering the same game.
Dan